Renthal Rear Sprockets are manufactured to extremely tight tolerances from 7075-T6 aluminum alloy which is 66% lighter than steel, yet incredibly durable. Advanced tooth profile, concentricity and accuracy of fit provide maximum power transfer and long-life. The combination of a very high-strength base material and an exceptionally hard-wearing surface results in significantly increased chainwheel life. Ultralight and 520 conversions available for certain models. ZX-14/06-11